Passengers are asked to plan ahead and check before they travel as some journeys may be longer as a result of essential upgrade work.
Buses will replace trains between Three Bridges and Horsham, and trains will run between Horsham and Bognor Regis.
Works will continue on the Redhill to Tonbridge line over the long weekend, ahead of its reopening on Tuesday, August 26 following a ten-day closure, with buses continuing to replace trains along the whole route.
Network Rail is currently working to replace 13 miles of high voltage power cables between Nutfield and Leigh, protecting the track from landslips, replacing worn-out rails near Edenbridge and undertaking maintenance works to improve the resilience of railway structures and equipment.
Near Edenbridge, where landslips have caused significant disruption to rail services in recent years, the railway embankment will be strengthened with a 360-metre-long steel wall either side of the track.
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